1. Field of the Invention
The present invention relates generally to an automotive air-conditioning apparatus, and more particularly, to an automotive air-conditioning apparatus having a cooling device driven by an automotive engine and a pre-cooling device driven by an energy source other than the automotive engine for pre-cooling an interior of a vehicle before the start of driving the vehicle.
2. Description of the Related Art
In general, an automotive air-conditioning apparatus is composed of a cooler incorporating a compressor driven by an engine. Accordingly, if the engine is stopped, the cooler is also stopped. On a very hot day in the heat of summer, the interior of a vehicle at rest with the engine being stopped reaches an excessively high temperature that greatly exceeds the external atmospheric temperature. This excessively high temperature may cause a variety of equipment or instruments in the interior of the vehicle to be broken down or deformed. Also, there is another problem in that, at the start of driving the vehicle, the steering wheel is to hot to grip, and even if the cooler is started, the interior temperature is hardly lowered, and is uncomfortable for the driver. Recently, for the purpose of preventing the global warming effect, the driver has been requested to stop the engine rather than allowing it to idle when the vehicle is at a temporary stop. However, most drivers would not stop the engine because the temperature of the interior of the vehicle would be abruptly elevated if the driver has stopped the engine even temporarily. In order to encourage the drive to stop the engine rather than allow it to idle, it is necessary for the interior of the vehicle to be maintained at a comfortable temperature while temporarily stopping the engine.
Japanese Utility Model Laid-Open No. Sho 58-136815 discloses an automotive air-conditioning apparatus having a cooling device driven by an engine and an auxiliary cooling device driven by an energy source other than the engine in order to meet the above-described demands. Namely, this conventional automotive air-conditioning apparatus is composed of a main cooling device driven by the engine and the auxiliary cooling device operated in the case where the engine is stopped or the air-conditioning driving ability by the engine output alone is insufficient so that a temperature of the interior of the vehicle becomes abnormally high. The auxiliary cooling device is provided with a solar battery in a light receivable portion of the vehicle. A thermoelectric element operated by the solar battery is provided in a duct. Further, a controller is provided for controlling the electric power supply to the thermoelectric element by detecting the external atmospheric temperature and the vehicle interior temperature and comparing those temperatures with the set temperatures.
This conventional automotive air-conditioning apparatus will no be described with reference to FIG. 4 which shows a circuit thereof. The vehicle interior is air-conditioned by the cooling device 20 while driving the engine during travel of the vehicle or even in a temporary stop of the vehicle. However, if the air-conditioning ability of the cooling device 20 is insufficient; the controller 30 turns on a switch S7 for supplying electric power from the solar battery 51 to the cooling thermoelectric element 52, thereby simultaneously performing cooling of the vehicle interior by the cooling device 20 and cooling thereof by the cooling thermoelectric element 52. During times when the vehicle engine is stopped, the controller 30 turns on the switch S7 to supply electric power from the solar battery 51, thereby air-conditioning the interior of the vehicle by only the cooling thermoelectric element 52. In this conventional automotive air-conditioning apparatus, in the sunshine, the cooling thermoelectric element 52 receives electric power from the solar battery 51 to air-condition the vehicle interior, thus functioning as an auxiliary cooling device. However, in the case where the vehicle is parked with the engine being stopped for a long period of time indoors or outdoors in the daytime in a cloudy or rainy day or at night in high summer, a sufficient amount of the electric power for driving the above-described auxiliary cooling device is not supplied by the solar battery. Accordingly the above-described auxiliary cooling device does not function as the cooler. Of course, a pre-cooling process for lowering the temperature of the interior of the vehicle at least down to the level of the external atmospheric temperature before starting the cooling device 20 to be driven by the engine 10 is not effected. Accordingly, in this conventional automotive air-conditioning apparatus, in the case where the vehicle is started after being parked for a long period of time, the temperature of the interior of the vehicle often greatly exceeds the external atmospheric temperature. Even if the cooling device is started, the temperature of the interior of the vehicle hardly lowers to the set temperature.
It is well known that, if ventilation is effected by a ventilation fan when the engine is off, the temperature of the interior of the vehicle is brought rather close to the external atmospheric temperature. According to some well-known data, in the case where the atmospheric temperature was about 30.degree. C. under the sunshine in high summer, the temperature of the interior of a solar car which was parked for a long time in the exterior parking lot reached about 60.degree. C. without ventilation, whereas the temperature was lowered down to about 45.degree. C. with only the ventilation by the ventilation fan. Thus, it is well known that ventilation is very effective for lowering the interior temperature. The ventilation fan device driven by the solar battery has been put into practical use and is already available on the market. However, in the case where the vehicle is parked with the engine being stopped for a long period of time indoors or outdoors in the daytime in a cloudy or rainy day or at night in high summer, a sufficient amount of electric power is not supplied by the solar battery for the above-described conventional ventilation fan device. Therefore, such device could not function as a ventilation fan.
Japanese Utility Model Laid-Open No. Sho 60-102121 discloses an example of a conventional automotive air-conditioning device which uses a cooling thermoelectric element as a cooling device that is driven by an energy source other than an engine and a regular battery loaded on a vehicle. In this conventional device, a heat absorbing section or a heat irradiation section of the cooling thermoelectric element is provided in a passage for communicating air introduced from the exterior of the vehicle or from the interior of the vehicle. A thermoelectric converting element for an electric power source for converting heat into electricity is provided in an exhaust pipe mounted on the engine so that The electric power generated by the above-described thermoelectric converting element is fed to the above-described cooling thermoelectric element. However, since the function of an conventional device as the electric power source is considerably degraded when the engine is stopped, this device could not serve as the air-conditioning device for the vehicle when the engine is stopped.
Incidentally, the conventional cooling device to be driven by the engine uses Freon gas. The device is designed so that is is a prerequisite that the vehicle interior is to be rapidly cooled when the vehicle is exposed under the sunshine and the vehicle interior is kept at a very high temperature. Accordingly, the structural components such as a compressor, a condenser and an evaporator become large in size. In addition, a large amount of Freon gas is needed. Also in view of the depletion of the ozone layer and the global warming effect due to the Freon gas, it is necessary to miniaturize the structural components of the automotive air-conditioning apparatus provided with a cooling device driven by the engine. However, an air-conditioning apparatus which meets this requirement has not been yet realized.